The application of a salt solution to reduce the amount of snow and ice from roads, sidewalks, driveways and other surfaces is a common industrial practice. Salt solution is generally created by mixing rock salt and water to produce a solution. The concentration of the solution may then adjusted by adding fresh water to dilute the mixture or adding salt to concentrate the mixture. A solution of approximately 23-27% by weight is efficient for removing ice and snow (where sodium chloride is the salt). At this concentration'range, the solution will melt ice and snow with an ambient temperature of approximately −10 degrees Fahrenheit. If the desired concentration is not maintained in the solution and applied in the correct amounts on the streets, accidents may occur.
One method of monitoring and adjusting the concentration of a solution is to measure the specific gravity of the solution and add fresh water to the solution until a desired specific gravity is met. This method thus correlates the specific gravity of the solution with the concentration of the solution. U.S. Pat. No. 6,439,252 discloses an apparatus and method for automatically producing large quantities of dissolved rock salt or calcium magnesium acetate (CMA) pellets in water for producing a salt solution to be used as a liquid deicer to be used for spraying roadways, sidewalks, driveways, and runways to melt snow and ice. An electronic hydrometer (a specific gravity measuring device) measures the specific gravity of the brine/water solution. If the specific gravity is too high or too low a valve is opened or closed to adjust the amount of fresh water to the mixture. In this manner the mixture is automatically adjusted to the salinity desired.
As mentioned above, methods for producing salt solutions that use specific gravity as an indicator of concentration correlate specific gravity to concentration. This correlation can, in some instances, be faulty. For example, solids such as silica, dirt, and other foreign material in the solution can affect the specific gravity of the solution and/or the reading of the measuring device. This may in turn lead to an undesired salt concentration level for the solution. In addition, measurements based on specific gravity generally are a series of separate measurements, spaced apart in time and process, rather than a continuous measurement as the progress proceeds.
Therefore, there is a need in the art for an apparatus and method that produces an accurate salt concentration level for a salt solution that is not dependent on measuring the solution's specific gravity.